Screen printing, lithographic printing, letterpress printing and intaglio printing are together known as the four great printing methods. Screen printing is completed by using screen printing equipment which consist of five elements, such as screen printing forme, scraper, ink, printing table and substrate, wherein, mesh of image area and mesh of non-image area are arranged in the screen printing forme, and the ink is capable of penetrating through the mesh of image area, but not incapable of penetrating through the mesh of non-image area.
The basic printing process by using the screen printing equipment comprises the follow steps of providing ink to one side of a screen printing forme when printing, applying a certain pressure on a part of screen printing forme having ink thereon by using the scraper to make the ink move towards another side, so as to allow the ink to be extruded from the mesh of image area onto the substrate by the scraper during the movement, lifting the scraper after it scrapes the entire forme, so as to lift the screen printing forme and scrape the ink back to its initial position. And this is an entire process of printing a monochrome image or pattern. In the process, the ink mark stays within a certain area due to the stickiness of ink, thereby forming the same image as that of the image area.
In the screen printing process, when printing, the screen printing forme generates reaction force, which is a resilience force, to the scraper due to its tension resulting from the fact that a certain gap is kept between the screen printing forme and the substrate, and due to the effect of resilience, it make a linear contact between the screen printing forme and the substrate that move relative to each other, with the other part of the screen printing forme being separated from the substrate, thereby causing rhegmagenesis of the ink and the screen printing forme, therefore, the screen printing may have higher dimensional accuracy. Moreover, in screen printing, the ink is transferred onto the substrate through the mesh of image area by extrusion of scraper so as to form the same image as the original one, which has the advantages of simple structure of equipment, easy operation and low cost. At present, the screen printing has been widely applied in printing, and the common screen printing products comprise color painting, posters, business cards, binding cover, product tags, dyeing textile, etc.
Nowadays, the screen printing technology has already been successfully applied on steel plate in order to form a thicker and more solid printing layer with a stronger stereo perception. However, the printing accuracy of screen printing is lower than that of intaglio printing technology, and in order to obtain more accurate printing patterns and designs and ensure that veneer has a thick and solid printing layer with a stronger stereo perception, many existing manufacturers try to combine the screen printing and the intaglio printing together by using intaglio printing equipment to make roller coating ground color patterns and then using the screen printing technology to obtain a thick and solid printing layer.
The roller coating equipment of the prior art comprises a feeding equipment, used for providing paints; a suction roller, whose circumferential surface is in connection with the feeding equipment, and has a plurality of recesses adapted for being filled with paints for forming an image area; and a rubber coating roller, with its circumferential surface in connection with the suction roller, and used for receiving and transferring the image area formed by the paints on the coating roller onto a steel plate to form desired multicolored patterns.
However, during the process of using the roller coating equipment, the applicant found out that the roller surface linear velocity of the suction roller and the rubber coating roller are frequently inconsistent with the process speed of the whole production line, and the whole production line is lack of a control system for on-line adjusting the rotation speed of the suction roller and the rubber coating roller, so the whole production line has to be stopped for adjustment after operation for a period of time, thus affecting the efficiency of the whole production line. If the production line is not stopped for adjustment, the steel plate transporting speed would be inconsistent with the roller surface linear velocity of each roller, thus frequently causing the steel plate unable to be coated at a designated position thereof. Besides, in order to print multicolor patterns, a plurality of roller coating equipments are required for coordinated operation. However, the above mentioned roller coating equipments in the prior art are lack of a control system for allowing a continuous production between adjacent roller coating equipments, so workers need observe by human eyes if a first roller coating equipment has completed coating of one color, and if yes, an adjacent roller coating unit will be started by manual work, thus it is unable to realize a continuous production between the adjacent roller coating equipments. At the same time, due to lack of the control system for adjusting the rotate speed of the suction roller and the coating roller, it is unable to realize error revision when misplacement occurs between the patterns printed by the adjacent roller coating equipments.
In conclusion, when roller coating primer paint by using roller coating equipment introduced in the screen printing production line, how to adjust the roller surface linear velocity of each roller of roller coating equipment so as to allow the roller surface linear velocity of each roller to be consistent with the process speed, and further improve the production efficiency has become a technical problem that needs to be solved.